Fluoroalkyl ethers and process for their manufacture

ABSTRACT

FLUORALKYL ALKYL ETHERS, ESPECIALLY PERFLUOROALKYL METHYL ALKYL ETHERS ARE PROVIDED. THEY CORRESPOND TO THE FORMULA   (H2-NF2M+N-1CM)-CH2-0-CQH2Q+1   IN WHICH M IS 4 TO 9, N IS AT MOST 2 AND Q IS AT MOST 4. THESE ETHERS ARE MANUFACTURED BY REACTING IN AN ANHYDROUS MEDIUM AND IN THE PRESENCE OF HYDROGEN HALIDE A CORRESPONDING FLUORALKANECARBOXYLIC ACID AND A CORRESPONDING DIALKYL ETHER WITH LITHIUM ALUMINUM HYDRIDE. THE FLUORALKYL ALKYL ETHERS ARE USEFUL AS HYDRAULIC LIQUIDS, AGENTS FOR CONFERRING OLEPHOBIC PROPERTIES OR INTERMEDIATE PRODUCTS, ESPECIALLY FOR THE MANUFACTURE OF FLUORALKYL VINYL ETHERS.

United States Patent Olfice FLUOROALKYL ETHERS AND PROCESS FOR THEIRMANUFACTURE Horst Jaeger, Bettingen, Switzerland, assignor to CibaLimited, Basel, Switzerland No Drawing. Filed Nov. 10, 1969, Ser. No.875,575 Claims priority, application Switzerland, Nov. 25, 1968, 17,515/68 Int. Cl. C07c 43/00 US. Cl. 260-614 F 7 Claims ABSTRACT OF THEDISCLOSURE Fluoralkyl alkyl ethers, especially perfluoralkyl methylalkyl ethers are provided. They correspond to the formula The subject ofthe invention is fiuoralkyl compounds. They correspond to the formula 12-n 2m+n1 m)' 2 q 2q+ 1 wherein m, n and q are positive integers, m is 4to 9, n is at most 2 and q is at most 4.

According to the invention these fluoroalkyl compounds are obtained byreacting, in an anhydrous medium and in the presence of hydrogen halide,fiuoralkanecarboxylic acids of formula wherein m and n have theindicated significance, and dialkyl ethers of formula wherein p denotesan integer having a value of 1 to 8 and q has the indicatedsignificance, with lithium aluminium hydride.

Fluoralkanecarboxylic acids of Formula 2 which can be used as startingsubstances are known. They for example correspond to the formula whereinx, y and 2 denote integers, x and y both are at most 2 and the totalnumber of the carbon atoms present in the molecule is at least 5 and atmost 10.

Accordingly, the following are for example used as starting substances:

(a) Perfluoralkanecarboxylic acids with an unbranched carbon chain,which correspond to the formula wherein k denotes an integer having avalue of 4 to 9, preferably an integer having a value of 6 to 9,especially perfiuorocaprylic acid '(C F C-OOH).

(b) Fluoralkanecarboxylic acids with an unbranched carbon chain whichcorrespond to the formula Patented Apr. 25, 1972 wherein k denotes aninteger having a value of 4 to 9, preferably an integer having a valueof 5 to 8.

(c) Perfiuoralkanecarboxylic acids with a chain which is branched at theend, which correspond to the formula (7) F 0 wherein k denotes aninteger having a value of 1 to 6.

Fluoralkanecarboxylic acids of Formulae 2 and 4 to 7 are known, and suchcarboxylic acids can furthermore be manufactured according to methodswhich are in themselves known.

The dialkyl ethers which serve as further starting substances in thepresent process can also contain branched or unbranched carbon atoms.They can be symmetrical or unsymmetrical and one of the two alkylresidues present in the molecule contains up to 8 carbon atoms and theother up to 4 carbon atoms. As examples, there may here be mentionedmethyl butyl ether, ethyl octyl ether and especially dialkyl ethers, ofwhich the alkyl groups contain 2 to 4 carbon atoms, such as dibutylether, but above all diethyl ether and diisopropyl ether.

The fluoralkanecarboxylic acids are reacted with the dialkyl ethers inan anhydrous medium. An organic solvent is appropriately used for thispurpose, and in particular advantageously an excess of the dialkylether, for example the 2-fold to 20-fold amount of dialkyl etherrelative to the amount of fluoralkanecarboxylic acid employed. It isfurthermore advisable to avoid contact of the reaction medium with airfrom the very start, for example by displacing the air in the reactionvessel by nitrogen or another inert gas.

Since the reaction takes place according to the equation [LiAlO ishypothetical, LiOH and Al(OH) being produced in the reaction mixture byhydrolysis] equimolecular amounts of fluoralkanecarboxylic acid anddialkyl ether are required, and one molecule of lithium aluminiumhydride is required per two carboxylic acid molecules or ethermolecules. It is appropriate to use an excess of this reducing agent,this excess however advantageously being selected to be not greater thanten times the theoretically required amount. The preferred molecularquantity ratio of fluoralkanecarboxylic acid to lithium aluminiumhydride is 1:1 to 1:2.

The reduction process according to the present method is carried out inthe presence of hydrogen halide, for example hydrogen iodide, hydrogenbromide, hydrogen chloride or especially however hydrogen fluoride.Hydrogen halide can be supplied in the gaseous state to the reactionmixture. It is however advisable, before com bining the substances whichare to be reacted with one another, to dissolve 0.01 to 5, preferably0.1 to 2 percent by weight of hydrogen halide in one of thesesubstances, for example in the ether or advantageously in thefluoralkanecarboxylic acid, and thereafter to combine this solutionslowly with the dialkyl ether which in turn contains the lithiumaluminium hydride. The reaction in general takes place slightlyexothermically so that a certain temperature rise results. It isadvisable to keep the temperature of the reaction mixture in the rangeof 10 C. to 30 C., if necessary by cooling or heating.

When the reaction has ended, the fluoralkyl-alkyl ether can be isolatedin the usual manner, for example by first decomposing unconsurnedlithium aluminium hydride as well as its primary reaction products withwater in the cold, separating off the non-aqueous part, optionally us- 3ing organic solvents, from the aqueous solution and precipitates, anddistilling off the organic solvent. The fluoralkyl-alkyl ethers aregenerally lquid at room temperature and can optionally be purified byvacuum diswith nitrogen (10 bubbles min). Thereafter 30 g. ofperfluorocaprylic acid (CF {-CF COOH, 0.0724mo1) containing /z% ofdissolved hydrogen fluoride gas are dissolved in 100 ml. of diethylether and added droptillation. wise in 60 minutes. The reactiontemperature hereupon The fluoralkyl-alkyl ethers of Formula 1 can foreX- rises from 18 C. to 28 C. The reaction is allowed to ample be usedas hydraulic liquids, agents for conferring finish over the course of 18hours. The mixture is then oleophobic properties, or intermediateproducts for the cooled by means of an ice/sodium chloride bath andmanufacture of the most diverse substances such as dyethe unreactedlithium aluminium hydride is decomposed stuffs, agents for conferringoleophobic properties and/ or with 7 ml. of distilled water. agents forconferring hydrophobic properties, and also In the course of this thereaction solution foams greatly. microbiocidal agents. In particular,the fluoralkyl-alkyl As soon as the reaction has subsided, 30 ml. of 80%ethers are suitable for use in further reactions, for eX- strengthsulphuric acid are added dropwise. Hereupon a ample for the manufactureof fluoralkyl vinyl ethers by fine, grey, granular precipitate forms.The ether phase reaction with chlorine and subsequent splitting off ofhy- 1 is separated from the aqueous phase and the aqueous drogenchloride. phase is extracted by shaking three times with 100 ml. It isknown that carboxylic acids can be reduced to the of diethyl ether at atime. The ether phases are comcorresponding alcohols by means of lithiumaluminium bined, dried and distilled. hydride. It is furthermore knownthat using the same re- Table II below provides information as to theyield, ducing agent, perfluoralcohols and perfiuoraldehydes are boilingpoint and mass spectrum of the n-perfi-uoroheptylproduced fromperfluorocarboxylic acids. It is therefore methyl-ethyl ether which canbe obtained. very surprising that fiuoralkyl-al'kyl ethers are obtainedin A proton resonance spectrum shows [recorded at 60 the same reactionif it is carried out in the presence of mc.] hydrogen halide and dialkylethers. agglsegcglentziggelstiin the examples which follow are percent-AM L 1 The procedure adopted in the following Examples 2 to 15 is alsoanalogous to that described in Example 1. The 5.86 g. (0.155 mol) oflithium aluminium hydride are starting products and their amounts aresummarised in dissolved in 350 ml. of absolute diethyl ether andinitially Table I. The data as to the end products are given inintroduced into a 750 ml. three-necked flask and covered Table 1.1.

TABLE I Amount of Fluoralkaneearboxylie acid Dialkyl ether LiAlH4Hydrogen halide Example No. G. M01 Ml. G. M01 Percent 1 30 0.0724Perfluorocaprylie acid--." 450 Diethyl ether 5.86 0.155 HF 21. 400Dibutyl ether 3.. Diethyl ether 2.93 0.077 4.. 5.86 0.155 5 Ethylbutylethen- 6.. 400 Diisopropyl ether- Diethyl etherw-H-perfluorononylcarboxylic acid.

12 23 0. 0556 Perfiuor-2ethylhexylcarboxylic acid. 2.64 0.01Perfluorovaleric acid 3. 97 0. 0126 Perflnorocaproic acid 400 20 0. 0483Perfiuoroeaprylic acid"...

TAB LE II Yield Boiling point, Percent 0. (un- Example No.Fluoroalkyl-alkyl ether G. of theory corrected) Mass spectrum 1nPerfluoroheptylmethyl ethyl ether 17. 5 56. 5 146-148 M=428; 427=M+H;413=M+ CH 399 ==M+ C2115; =0 CHCHa; 59= CHzO-CH2CH3.

2 n-Perfiuoroheptylmethyl n-but-yl ether 1. 71 5. 16 1 -62 M=456; 455=M+H; 441=M+CH 427=M+ CzHa; 87= GHQ-0- 3 n-Perfluoroheptyhnethyl ethylether 12. 4 40 2 60-64 See Example 1.

6 n-Perfluoroheptylmethyl isopropyl ether l9. 6 60. 7 4 67-69 M =442;441=M+H; 427=442+ CH /CH 43= (-HSH 7 n-Perfiuoroheptylmethyl ethyl etherSee Example 1.

11 w-H-pertluoroctylmethyl ethyl ether 13. 9 Mgififi vgfitlgll-l-fl;455=M+ CH1;

12 (n-Perfluor-2-ethylpentyD-methyl ethyl ether. 11. 0 M=428;decomposition series similar to that in Example 1; difierentintensities.

13 n-Perfluoropentylmethyl ethyl ether-.. 61.15 -97 M=278.

14--. n-Perfluoroheptylmethyl ethyl ether 60. 2 106-107 M=328.

15 {n-Perfluoroheptylmethyl ethyl ether 15. 4 103-105 M=428.

""""""" Perfiuoroetanol- 4. 81 146-147 M=400.

EXAMPLE 16 (16.1) 43 g. (0.1 mol) of perfiuoroheptylmethyl ethyl etherare dissolved in 50 ml. of carbon tetrachloride. 11 g. of chlorine arethen passed through the solution over the course of 90 minutes in a 200ml. flask having a gas inlet tube, thermometer, reflux condenser andstirrer. During this time the reaction vessel is irradiated by means ofa 250 watt tungsten lamp, in the course of which the temperature risesfrom 23 C. to 71 C., this being mainly caused by the radiant heat of theincandescent lamp. The reaction product is fractionally distilled. Afterseparating off the carbon tetrachloride, 31.10 g. of reaction productare obtained. This product cannot be separated into pure fractions, butazeotropic mixtures of r varying composition are produced. The followingcom- 0 position of the reaction product amount to 31.10 g. is found bygas-chromatographic separation of analytical amounts:

Percent 14.13 g. perfluoroheptylmethyl ethyl ether 45.43 10.8 g.perfluoroheptylmethyl a-chloroethyl ether 34.73 4.95 g.perfluoroheptylmethyl oc-diChlOIOCthYl ether 15.92 1.22 g.di-perfluoroheptylmethyl-ethyl-acetate+diperfiuoroheptylmethyl-a-chloroethyl-acetal3.92 0

The conversion of the starting material into perfluoroheptylmethylot-chloroethyl ether is 10.8/46.2=23.37% of theory.

The individual new compounds are identified by the mass spectrum. (a) 0F(CF CH OCHClCH Perfluoroheptylmethyl u-chlorethyl ether M=462, 464 3! 0The intensity ratios agree with the isotope distribution of C1 and Cl447=M +CH 427=M4 2+Cl 5 40 In the nuclear resonance spectrum thefollowing can be detected (60 mc.) i i or ill-CH bands between 5.2 to4.8 p.p.m. C Fz-EEz-O bands between 4.3 to 3.5 p.p.m.

(SH-2E; bands between 1.3 to 1.45 p.p.m.

(b OF3' 2) 5CH2-OCC12CH3 Penfluoroheptylmethyl a-dichlorethyl ether461=496C1 460=496HC1 M=496-l-the isotope peaks expected for 2 Cl In thenuclear resonance spectrum the following can be detected mc.) CE-g-Obands between 4.8 to 3.8 ppm. CI CH 2.08 ppm.

(0) Acetals as secondary reaction products CF3(C 1 95-01120 M 60 CHI-CH3825 =826+H 811=826+CH3 C F;(C Foe-C1120 427=826 +399 M:399CF3(CF2)6CHg-O M=860+862 63 CCl-CH 859=860+H s25=se0+o1,5 s27) c 1?;(0F2)5CH2O 810=860+CH Cl 5(812) The production of acetals can bereproduced by the following equation:

(ROH O) CHCH +C1CH CH It is known that in an ether, chlorine in thea-position can be easily split off.

(16.2) 0.5 g. of perfiuoroheptylmethyl a-chlorethyl ether is mixed with10 ml. of 25% strength ammonia and shaken. The lower phase is separatedfrom the aqueous phase, twice washed with 1 ml. of water, taken up inether and dried with a little sodium sulphate (anhydrous). The ether isevaporated and a mass spectrum of the etherfree residue (0.3 g.) isrecorded. This shows:

The same result is obtained if 0.5 g. of penfiuoroheptylmethyla-chlorethyl ether, in a long tube sealed at the bottom, is heated to250 C. in an oil bath for 30 minutes, or if in the above experiment 10m1. of 30% strength potassium hydroxide solution are used instead of 10ml. of 25 strength ammonia.

:EXAMPLE 17 EXAMPLE 18 Perfluoroheptylmethyl ethyl ether manufacturedaccording to Example 1 is circulated for 8 hours at 700 C. in acirculation apparatus which contains. a steel spiral (2 mm. diameter)heated to 700 C. and also contains a spiral (2 mm. diameter) cooled to 0C. The material can be recovered unchanged apart from the lossesconditioned by the experimental system. The material is not discoloured.The gas chromatogram and mass spectrum of the starting material and ofthe circulating product are identical.

I claim:

1. A process for the manufacture of a fiuoralkyl alkyl ether of theformula in which m, n and q denote positive integers, m is 4 to 9, n isat most 2 and q is at most 4, which comprises reacting in an anhydrousmedium in the absence of air at a temperature of 10 to 30 C., afluoralkanecarboxylic acid of the formula 2n 2m+n 1C )-COOH in which mand n have the meanings above, and 2 to 20 fold amount relative to theamount of fl'uoroalkane carboxylic acid employed of a dialkyl ether ofthe formula in which p is an integer having a value of l to 8 and q hasthe above meaning, with lithium aluminum hydride in the presence ofhydrogen halide.

2. A process according to claim 1, which comprises using as startingsubstance a fiuoroalkane carboxylic acid of the formula in which x, yand z are integers, x and y are each at most 2, z is 1 to 9 and thetotal number of the carbon atoms in the molecule is at least 5 and atmost 10.

3. A process according to claim 1, which comprises using as startingsubstance at fluoroalkane carboxylic acid of the formula in which k isan integer having a value of 4 to 9..

4. A process according to claim 1, which comprises using as startingsubstance a diuoroalkane carboxylic acid of the formula in which k is aninteger having a value of 4 to 9.

5. A process according to claim 1, which comprises using as startingsubstance a dialkyl ether of which the alkyl groups each contain 2. to 4carbon atoms.

6. A process according to claim 1, which comprises reactingperfluorocaprylic acid and diethyl ether.

7. A process according to claim 1, which comprises using as startingsubstance a fluoroalkane carboxylic acid of the formula References CitedUNITED STATES PATENTS 3,291,844 12/1966 Watson i 260-4514 F 3,420,8401/1969 Tesoro et a1. 260614 F X OTHER REFERENCES Lu et al., Chem. Abstn,48 1584 (Anesthesiology 14,

Henne et al., J. Am. Chem. Soc., 72, pp. 4378-4380, 1950.

HOWARD T. MARS, Primary Examiner US. Cl. X.R.

